Previous investigations have placed major emphasis on the biosynthetic events leading to the appearance of adenovirus subunits. The proposed research will examine 1) the molecular events which prepare the infecting viral genome for transcription and replication (i.e. the final reactions in viral eclipse); and 2) the maturation of viral capsid proteins and the assembly of the virion from its constituent DNA and proteins. In vivo and in vitro experiments will be devised to study viral eclipse. The chemical and physical structures of the capsid proteins will be studied to furnish possible models of folding and assembly of the multimeric capsid proteins. To study maturation of adenovirus particles in vitro assembly of the viral DNA and proteins will be attempted, and conditionally lethal assembly mutants will be selected. Types 2,3,5, and 12 adenoviruses will be employed.